Two INpact M.2 PROFINET IRT cards on the same subnet exhibiting strange behavior


I have two INpact M.2 PROFINET IRT cards. They reside in two units of our custom hardware. They are on the same subnet (only the 4th octet of their addresses differ):

Card 1:
Netmask: 255:255:255:0

Card 2:
Netmask: 255:255:255:0

As part of the initialization process in our code, we call the following to obtain the card’s IP address:

ABCC_GetAttribute(psMsg, ABP_OBJ_NUM_NC, 3, ABP_NC_VAR_IA_VALUE, ABCC_GetNewSourceId());

We sometimes see this sequence of behavior:

  1. When a card is initialized, we see that the returned attribute is the IP address value of the other card.
  2. When the other card initializes, its IP address is, presumably because of Address Conflict Detection.

This is rather strange behavior, and we would like to better understand why this is happening. Any help is appreciated.

  • Joseph

We were able to figure out our problem. The PLC was assigning the IP tuples based on the Station Name (which we had not realized were set to the same value for both cards).

1 Like

Great - thank you for the update!